The present invention relates to automotive roadwheels and more particularly pertains to a wheel and method for achieving a rotationally balanced tire/wheel assembly.
Proper rotational balance of an automobile's tires is essential in order to provide a smooth ride, optimize handling characteristics, minimize wear and tear to the vehicle and extend the service life of the tires. A tire is normally balanced after its mounting to a wheel by the attachment of weight to the wheel. The balancing procedure typically comprises the steps of spinning the tire/wheel assembly up to speed, measuring forces generated by any imbalance, determining the amount of weight and the precise placement of such weight necessary to counteract the measured forces and crimping the required weight to the wheel's outer edges or adhesively securing the weights to the wheel. The assembly is then again spun up to speed to confirm that proper balance has been achieved. Occasionally, the entire balancing procedure must be repeated if a further readjustment is found to be necessary.
Repeating the above-described procedure for every tire of every vehicle manufactured in a modern high-speed automobile assembly line amounts to a significant effort. Any reduction in such an expense would of course be advantageous. Reducing the amount of weight necessary or obviating the need to actually add balancing weight to a significant portion of a manufacturing line's throughput would in fact constitute such an improvement.
Eliminating the balancing weights from a wheel provides the secondary benefit of enhancing the aesthetic appearance of the wheel as the lead weights normally crimped onto or adhered to the outboard side of the wheel are generally considered unsightly.
Although wheels can be produced to very exacting standards with respect to rotational balance, it is much more difficult if not impossible to manufacture a balanced tire. The complex internal structure of modern tires defies efforts to achieve an even weight distribution from the outset while the elastic nature of the tire makes it difficult to predict, let alone compensate for, the distortion and its commensurate effect on balance caused by the extremely high g-forces a tire is subjected to at highway speeds. Producing a finely balanced tire to be mounted to a finely balanced wheel in order to yield a balanced tire/wheel assembly is therefore not a viable approach towards minimizing the labor normally expended in balancing an automobile's tires. Tire manufacturers do however have the ability to dynamically test each tire for imbalance and mark the tire carcass to indicate the location of the highest or lowest concentration of weight.
An alternative approach is therefore called for that provides a rotationally balanced tire/wheel assembly which requires only a minimal amount of weight addition and in a significant number of incidents, obviates the need to add any extraneous balancing weights whatsoever.